A forklift potential energy recovery system, method, and forklift based on high and low pressure pump motor oil replenishment.

Abstract

This invention relates to potential energy recovery technology during the lifting or lowering of a forklift, specifically a forklift potential energy recovery system, method, and forklift based on high and low pressure pump motor oil replenishment. It includes a lifting oil circuit, a lowering oil circuit, a potential energy recovery oil circuit, and an auxiliary oil replenishment oil circuit. The lifting oil circuit includes a hydraulic oil tank (1); the hydraulic oil tank (1) is connected to the inlet of a hydraulic pump (2); the shaft of the hydraulic pump (2) is driven to a motor (3); the outlet of the hydraulic pump (2) is connected to the inlet of a first check valve (4); the outlet of the first check valve (4) is connected to the inlet of a throttle valve (6); the outlet of the throttle valve (6) is connected to the P port of a three-position four-way solenoid directional valve (7); the A port of the three-position four-way solenoid directional valve (7) is connected to the rodless chamber of a first hydraulic cylinder (8) and a second hydraulic cylinder (9), wherein the first hydraulic cylinder (8) and the second hydraulic cylinder (9) are used to drive the forks to rise.

Description

Technical Field

[0001] This invention relates to potential energy recovery technology during the lifting or lowering of forklifts, specifically a forklift potential energy recovery system, method, and forklift based on high and low pressure pump motor oil replenishment. Background Technology

[0002] Traditional forklifts are mostly powered by internal combustion engines, which has long had significant drawbacks: on the one hand, energy consumption remains high, with fuel costs accounting for a significant proportion of forklift operating costs, and the continuous rise in global energy prices further exacerbates the operational burden on enterprises; on the other hand, internal combustion engines continuously emit exhaust gases during operation, polluting the working environment and surrounding ecology, which contradicts the current trend of energy-saving and environmentally friendly industrial development. They also suffer from low energy efficiency and slow dynamic response speed, making it difficult to meet the high-efficiency and low-carbon operational needs of modern logistics.

[0003] Against the backdrop of continuously rising energy costs and increasingly stringent energy conservation and environmental protection requirements, improving the energy efficiency and utilization rate of forklifts has become an urgent need for the high-quality development of the logistics equipment industry. In this context, the industry has gradually focused on the research and development of forklift energy recovery technology, with the recovery and reuse of gravitational potential energy becoming a key research focus. Although forklift energy recovery technologies have made some progress, in practical applications, forklift lifting systems still have significant shortcomings in core dimensions such as precise energy consumption control, energy recovery and utilization rate, and system dynamic response speed. Breakthroughs through technological optimization are urgently needed to drive the forklift industry towards low-carbon, high-efficiency, and energy-saving upgrades. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a forklift potential energy recovery system, method, and forklift based on high and low pressure pump motor oil replenishment, in order to improve the energy utilization rate and dynamic response speed of forklift operations.

[0005] This invention provides a forklift potential energy recovery system based on high and low pressure pump motor oil replenishment, comprising a lifting oil circuit, a lowering oil circuit, a potential energy recovery oil circuit, and an auxiliary oil replenishment oil circuit;

[0006] The lifting hydraulic circuit includes a hydraulic oil tank 1, a hydraulic pump 2, an electric motor 3, a first check valve 4, a throttle valve 6, and a three-position four-way solenoid directional valve 7. The hydraulic oil tank 1 is connected to the oil inlet of the hydraulic pump 2. The shaft of the hydraulic pump 2 is connected to the electric motor 3. The oil outlet of the hydraulic pump 2 is connected to the oil inlet of the first check valve 4. The oil outlet of the first check valve 4 is connected to the inlet of the throttle valve 6. The outlet of the throttle valve 6 is connected to the P port of the three-position four-way solenoid directional valve 7. The A port of the three-position four-way solenoid directional valve 7 is connected to the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9. The first hydraulic cylinder 8 and the second hydraulic cylinder 9 are used to drive the forks to rise. The lowering hydraulic circuit includes a hydraulic oil tank 1, a hydraulic pump 2, an electric motor 3, a first check valve 4, a throttle valve 6, and a three-position four-way solenoid directional valve 7; the B port of the three-position four-way solenoid directional valve 7 is connected to the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9; wherein, the first hydraulic cylinder 8 and the second hydraulic cylinder 9 are used to drive the forks to lower. The potential energy recovery oil circuit includes a two-position three-way solenoid directional valve 10, a first two-position two-way solenoid directional valve 12, a second check valve 13, a five-position four-way hydraulic directional valve 14, a high-pressure pump motor 15, and a low-pressure pump motor 17; the T-port of the three-position four-way solenoid directional valve 7 is connected to the oil inlet of the two-position three-way solenoid directional valve 10; the oil outlet of the two-position three-way solenoid directional valve 10 is connected to the oil inlet of the first two-position two-way solenoid directional valve 12; the oil outlet of the first two-position two-way solenoid directional valve 12 is connected to the oil inlet of the second check valve 13; the five-position four-way hydraulic directional valve 14 is sequentially connected to the oil outlet of the second check valve 13, the oil outlet of the high-pressure pump motor 15, and the oil outlet of the low-pressure pump motor 17; the oil inlets of the high-pressure pump motor 15 and the low-pressure pump motor 17 are connected to the hydraulic oil tank 1.

[0007] The auxiliary oil supply circuit includes a two-position three-way solenoid directional valve 10, a booster 11, a first two-position two-way solenoid directional valve 12, a second check valve 13, a five-position four-way hydraulic directional valve 14, a second two-position two-way solenoid directional valve 19, and a third check valve 20. The five-position four-way hydraulic directional valve 14 is sequentially connected to the oil outlet of the second check valve 13 and the oil inlet of the second two-position two-way solenoid directional valve 19. The oil outlet of the second two-position two-way solenoid directional valve 19 is connected to the oil inlet of the third check valve 20, and the oil outlet of the third check valve 20 is connected to the oil outlet of the first check valve 4.

[0008] Preferably, the lifting oil circuit and the lowering oil circuit further include a first relief valve 5, the oil inlet of the first relief valve 5 being connected to the oil outlet of the first check valve 4, and the oil outlet of the first relief valve 5 being connected to the hydraulic oil tank 1.

[0009] Preferably, the first hydraulic cylinder 8 and the second hydraulic cylinder 9 are arranged in parallel, the rod chamber of the first hydraulic cylinder 8 is connected to the rod chamber of the second hydraulic cylinder 9, and the rodless chamber of the first hydraulic cylinder 8 is connected to the rodless chamber of the second hydraulic cylinder 9.

[0010] Preferably, the potential energy recovery oil circuit further includes a second overflow valve 16, the oil inlet of the second overflow valve 16 being connected to the oil outlet of the high-pressure pump motor 15, and the oil outlet of the second overflow valve 16 being connected to the hydraulic oil tank 1.

[0011] Preferably, the potential energy recovery oil circuit further includes a third relief valve 18, the oil inlet of the third relief valve 18 being connected to the oil outlet of the low-pressure pump motor 17, and the oil outlet of the third relief valve 18 being connected to the hydraulic oil tank.

[0012] A control method for a forklift potential energy recovery system based on high and low pressure pump motor oil replenishment, which adopts the forklift potential energy recovery system as described above, wherein the control method for lifting the forklift forks is specifically as follows: A1. Use a sensor to determine the relationship between the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 and a first preset value and a second preset value. The first preset value is the low pressure threshold of the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9, and the second preset value is the medium pressure threshold of the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9. A2. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 does not exceed the first preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the fourth position, and the second two-position two-way solenoid directional valve 19 is opened so that the high-pressure pump motor 15 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, step A4 is executed directly. A3. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 is between the first preset value and the second preset value, control the five-position four-way hydraulic directional valve 14 to work in the fifth position and open the second two-position two-way solenoid directional valve 19 so that the low-pressure pump motor 17 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, directly execute step A4. A4. Connect the oil inlet of the three-position four-way solenoid directional valve 7 to the working outlet. The electric motor drives the hydraulic pump to supply the hydraulic oil in the hydraulic oil tank 1 to the oil circuit. The hydraulic oil passes through the first check valve 4, the throttle valve 6, and the three-position four-way solenoid directional valve 7 to enter the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 to realize the lifting motion of the forklift forks. A5. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 exceeds the second preset value, the first two-position two-way solenoid directional valve 12 is closed, the five-position four-way hydraulic directional valve 14 is controlled to work in the first position, and the second two-position two-way solenoid directional valve 19 is opened so that the hydraulic oil pressurized by the booster 11 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment.

[0013] Preferably, the control method for lowering the forklift forks is as follows: B1. Use a sensor to determine the relationship between the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 and the third preset value and the fourth preset value. The third preset value is the low pressure threshold of the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9, and the fourth preset value is the medium pressure threshold of the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9. B2. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 does not exceed the third preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the fourth position, and the second two-position two-way solenoid directional valve 19 is opened so that the high-pressure pump motor 15 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, step B4 is executed directly. B3. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 is between the third preset value and the fourth preset value, control the five-position four-way hydraulic directional valve 14 to work in the fifth position and open the second two-position two-way solenoid directional valve 19 so that the low-pressure pump motor 17 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, directly execute step B4. B4. Connect the oil inlet of the three-position four-way solenoid directional valve 7 to the working outlet. The electric motor drives the hydraulic pump to supply the hydraulic oil in the hydraulic oil tank 1 to the oil circuit. The hydraulic oil passes through the first check valve 4, the throttle valve 6, and the three-position four-way solenoid directional valve 7 to enter the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 to realize the forklift fork lowering movement. B5. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 exceeds the fourth preset value, the first two-position two-way solenoid directional valve 12 is closed, the five-position four-way hydraulic directional valve 14 is controlled to work in the first position, and the second two-position two-way solenoid directional valve 19 is opened so that the hydraulic oil pressurized by the booster 11 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment.

[0014] Preferably, the control method for recovering potential energy from the low-pressure pump motor is as follows: C1. Use sensors to determine the relationship between the load of the forklift and the fifth and sixth preset values, and to determine whether the pressure of the low-pressure pump motor 17 is less than the seventh preset value. The fifth preset value is the low-pressure threshold of the forklift load, the sixth preset value is the medium-pressure threshold of the forklift load, and the seventh preset value is the maximum energy storage threshold of the low-pressure pump motor 17. C2. When it is determined that the load of the forklift is within the range of the fifth and sixth preset values, and the pressure of the low-pressure pump motor 17 is less than the seventh preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the third position, the first and second-position two-way solenoid directional valve 12 is opened, and the working outlet and return oil outlet of the three-position four-way solenoid directional valve 7 are connected, so that the hydraulic oil in the load of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 enters the low-pressure pump motor 17 under the action of the gravity of the goods through the three-position four-way solenoid directional valve 7, the two-position three-way solenoid directional valve 10, the first and second-position two-way solenoid directional valve 12, the second check valve 13 and the five-position four-way hydraulic directional valve 14, thereby realizing the recovery of gravitational potential energy. C3. When it is determined that the forklift load is less than the fifth preset value, open the two-position three-way solenoid directional valve 10 and connect the working outlet and return oil outlet of the three-position four-way solenoid directional valve 7, so that the hydraulic oil in the load of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 flows directly back to the hydraulic oil tank through the three-position four-way solenoid directional valve 7 and the two-position three-way solenoid directional valve 10 under the action of gravity.

[0015] Preferably, the control method for recovering potential energy from the high-pressure pump motor is as follows: D1. Use sensors to determine the relationship between the load of the forklift and the fifth and sixth preset values, and determine whether the pressure of the high-pressure pump motor 15 is less than the eighth preset value, which is the highest threshold for the energy stored in the high-pressure pump motor. D2. When it is determined that the load of the forklift exceeds the sixth preset value and the pressure of the high-pressure pump motor 15 is less than the eighth preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the second position, the first two-position two-way solenoid directional valve 12 is opened, and the working outlet and return oil outlet of the three-position four-way solenoid directional valve 7 are connected, so that the hydraulic oil in the load of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 enters the high-pressure pump motor 15 under the action of the gravity of the cargo through the three-position four-way solenoid directional valve 7, the two-position three-way solenoid directional valve 10, the first two-position two-way solenoid directional valve 12, the second check valve 13 and the five-position four-way hydraulic directional valve 14, so as to realize the recovery of gravitational potential energy; otherwise, execute C3.

[0016] Preferably, C2 specifically includes: C21. When it is determined that the load of the forklift is within the range of the fifth preset value and the sixth preset value, and the pressure of the low-pressure pump motor 17 is less than the seventh preset value, it is further determined whether the difference between the pressure of the forklift load and the pressure of the low-pressure pump motor 17 exceeds the ninth preset value. The ninth preset value is the minimum threshold value representing the difference between the forklift load and the low-pressure pump motor pressure. C22. Further determine that when the difference between the pressure of the forklift load and the pressure of the low-pressure pump motor 17 exceeds the ninth preset value, open the first two-position two-way solenoid directional valve 12 and control the five-position four-way hydraulic directional valve 14 to work in the third position, so that it connects in sequence to the oil outlet of the second check valve 13 and the oil outlet of the low-pressure pump motor 17, so that the hydraulic oil flows back to the low-pressure pump motor 17 through the first two-position two-way solenoid directional valve 12 and the five-position four-way hydraulic directional valve 14.

[0017] Preferably, D2 specifically includes: D21. When it is determined that the load of the forklift exceeds the sixth preset value and the pressure of the high-pressure pump motor 15 is less than the eighth preset value, it is further determined whether the difference between the pressure of the forklift load and the pressure of the high-pressure pump motor 15 exceeds the tenth preset value. The tenth preset value is the minimum threshold representing the pressure difference between the forklift load and the high-pressure pump motor. D22. Further determine that when the difference between the pressure of the forklift load and the pressure of the high-pressure pump motor 15 exceeds the tenth preset value, open the first two-position two-way solenoid directional valve 12 and control the five-position four-way hydraulic directional valve 14 to work in the second position, so that it connects in sequence to the oil outlet of the second check valve 13 and the oil outlet of the high-pressure pump motor 15, so that the hydraulic oil flows back to the high-pressure pump motor 15 through the first two-position two-way solenoid directional valve 12 and the five-position four-way hydraulic directional valve 14.

[0018] A forklift includes a forklift potential energy recovery system based on high and low pressure pump motor oil replenishment as described above.

[0019] The present invention has the following beneficial effects: The forklift potential energy recovery system based on high and low pressure pump motor oil replenishment provided by the present invention, on the basis of the hydraulic drive system jointly realized by the electric motor and the hydraulic pump, introduces the energy-saving technology of high and low pressure pump motor to realize hydraulic oil replenishment and energy recovery, further improving the high frequency dynamic response and energy recovery capability of the forklift hydraulic system, and realizing the efficient and stable operation of the system.

[0020] Furthermore, by using a two-position two-way solenoid directional valve and a five-position four-way hydraulic directional valve to separate the potential energy recovery oil circuits under different oil pressures, pump motors with different initial pressures are selected to operate according to different hydraulic oil pressures. At the same time, combined with the booster effect of the intensifier, the recovered energy can be quickly reused, optimizing the dynamic response characteristics of the system, improving the smoothness of operation, and adapting to operating scenarios with high dynamic performance requirements. Moreover, through a precise control strategy of multi-stage pressure detection and valve group coordination, the system achieves graded energy storage of high and low pressure pump motors and intelligent switching of multi-source auxiliary oil replenishment, ensuring the stable and efficient operation of the system under different load conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the forklift potential energy recovery system based on high and low pressure pump motor oil replenishment according to the present invention.

[0023] In the diagram: 1-Hydraulic oil tank, 2-Hydraulic pump, 3-Electric motor, 4-First check valve, 5-First relief valve, 6-Throttle valve, 7-Three-position four-way solenoid directional valve, 8-First hydraulic cylinder, 9-Second hydraulic cylinder, 10-Two-position three-way solenoid directional valve, 11-Intensifier, 12-First two-position two-way solenoid directional valve, 13-Second check valve, 14-Five-position four-way hydraulic directional valve, 15-High-pressure pump motor, 16-Second relief valve, 17-Low-pressure pump motor, 18-Third relief valve, 19-Second two-position two-way solenoid directional valve, 20-Third check valve. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example The following are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the following embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

[0026] Reference manual attached Figure 1 As shown, this embodiment of the invention provides a forklift potential energy recovery system based on high and low pressure pump motor oil replenishment, which includes a lifting oil circuit, a lowering oil circuit, a potential energy recovery oil circuit and an auxiliary oil replenishment oil circuit.

[0027] The lifting hydraulic circuit includes a hydraulic oil tank 1; the hydraulic oil tank 1 is connected to the oil inlet of the hydraulic pump 2; the shaft of the hydraulic pump 2 is driven to the motor 3; the oil outlet of the hydraulic pump 2 is connected to the oil inlet of the first check valve 4; the oil outlet of the first check valve 4 is connected to the inlet of the throttle valve 6; the outlet of the throttle valve 6 is connected to the P port of the three-position four-way solenoid directional valve 7; the A port of the three-position four-way solenoid directional valve 7 is connected to the rodless chamber of the hydraulic cylinder; wherein, the first hydraulic cylinder 8 and the second hydraulic cylinder 9 are used to drive the forks to rise.

[0028] The lowering oil circuit includes a hydraulic oil tank 1; the hydraulic oil tank 1 is connected to the oil inlet of the hydraulic pump 2; the shaft of the hydraulic pump 2 is driven to the motor 3; the oil outlet of the hydraulic pump 2 is connected to the oil inlet of the first check valve 4; the oil outlet of the first check valve 4 is connected to the inlet of the throttle valve 6; the outlet of the throttle valve 6 is connected to the P port of the three-position four-way solenoid directional valve 7; the B port of the three-position four-way solenoid directional valve 7 is connected to the rod chamber of the hydraulic cylinder; wherein, the first hydraulic cylinder 8 and the second hydraulic cylinder 9 are used to drive the forks to lower.

[0029] Reference manual attached Figure 1 Based on the above embodiments, in an optional embodiment of the present invention, the number of hydraulic cylinders is two, namely a first hydraulic cylinder 8 and a second hydraulic cylinder 9. The first hydraulic cylinder 8 and the second hydraulic cylinder 9 are arranged in parallel, with the rod-side chamber of the first hydraulic cylinder 8 connected to the rod-side chamber of the second hydraulic cylinder 9, and the rodless chamber of the first hydraulic cylinder 8 connected to the rodless chamber of the second hydraulic cylinder 9. Specifically, the arrangement of the two hydraulic cylinders in parallel can generate a balanced driving force on the forklift forks, making the force more even and the operation more stable during the lifting and lowering of the forks. This effectively avoids the uneven load and tilting problems that are prone to occur when driven by a single cylinder, reduces abnormal wear of the cylinder body and piston rod, and extends the service life of the hydraulic actuators. At the same time, the synchronous drive of the two cylinders can also improve the stability of the lifting and lowering of the forks, avoid the displacement of the goods due to unilateral force, and further improve the safety and reliability of forklift operation.

[0030] Reference manual attached Figure 1 The lifting and lowering oil circuits also include a first relief valve 5 and a throttle valve 6. The inlet of the first relief valve 5 is connected to the outlet of the first check valve 4. The outlet of the first relief valve 5 is connected to the hydraulic oil tank. The throttle valve 6 is connected between the P port of the three-position four-way solenoid directional valve 7 and the outlet of the first check valve 4. Specifically, the first relief valve 5 can reliably protect the lifting oil circuit from overpressure, promptly releasing excessive pressure in the oil circuit and effectively preventing malfunctions caused by excessive pressure. The throttle valve 6 can precisely adjust the flow rate of the hydraulic oil, thereby smoothly controlling the lifting and lowering rate of the hydraulic cylinder, avoiding sudden speed changes in the cylinder, ensuring the smoothness of the fork lifting action, and possessing good practicality.

[0031] The potential energy recovery oil circuit includes a two-position three-way solenoid directional valve 10, a first two-position two-way solenoid directional valve 12, a second check valve 13, a five-position four-way hydraulic directional valve 14, a high-pressure pump motor 15, and a low-pressure pump motor 17. The T-port of the three-position four-way solenoid directional valve 7 is connected to the inlet of the two-position three-way solenoid directional valve 10. The outlet of the two-position three-way solenoid directional valve 10 is connected to the inlet of the first two-position two-way solenoid directional valve 12; the outlet of the first two-position two-way solenoid directional valve 12 is connected to the inlet of the second check valve 13; the five-position four-way hydraulic directional valve 14 is sequentially connected to the outlet of the second check valve 13, the outlet of the high-pressure pump motor 15, and the outlet of the low-pressure pump motor 17; the inlets of the high-pressure pump motor 15 and the low-pressure pump motor 17 are connected to the hydraulic oil tank 1.

[0032] Reference manual attached Figure 1 Based on the above embodiments, in an optional embodiment of the present invention, the potential energy recovery oil circuit further includes a second relief valve 16 and a third relief valve 18. The inlet of the second relief valve 16 is connected to the outlet of the high-pressure pump motor 15, and the outlet is connected to the hydraulic oil tank 1; the inlet of the third relief valve 18 is connected to the outlet of the low-pressure pump motor 17, and the outlet is connected to the hydraulic oil tank 1; specifically, the second relief valve 16 and the third relief valve 18 can prevent excessive pressure of the pump motor during potential energy recovery.

[0033] The auxiliary oil replenishment circuit includes a two-position three-way solenoid directional valve 10, a booster 11, a first two-position two-way solenoid directional valve 12, a second check valve 13, a five-position four-way hydraulic directional valve 14, a second two-position two-way solenoid directional valve 19, and a third check valve 20. The T port of the three-position four-way solenoid directional valve 7 is connected to the inlet of the two-position three-way solenoid directional valve 10; the outlet of the two-position three-way solenoid directional valve 10 is connected to the inlet of the first two-position two-way solenoid directional valve 12 and the inlet of the booster 11; the outlet of the first two-position two-way solenoid directional valve 12 and the outlet of the booster 11 are connected to the oil inlet of the second check valve 13; the five-position four-way hydraulic directional valve is sequentially connected to the oil outlet of the second check valve 13 and the inlet of the second two-position two-way solenoid directional valve 19; the outlet of the second two-position two-way solenoid directional valve 19 is connected to the oil inlet of the third check valve 20, and the oil outlet of the third check valve is connected to the oil outlet of the first check valve.

[0034] In this embodiment, the inlet of the booster 11 is connected to the oil inlet of the first two-position two-way solenoid directional valve 12, and the outlet of the booster 11 is connected to the oil outlet of the first two-position two-way solenoid directional valve 12; the oil inlet of the second check valve 13 is connected to the outlet of the booster 11, and the oil outlet of the second check valve 13 is connected to the five-position four-way hydraulic directional valve 14; it can be understood that installing the second check valve 13 at the inlet or outlet of the booster 11 is equivalent, and both solutions fall within the protection scope of this invention.

[0035] The present invention provides a forklift potential energy recovery system based on high and low pressure pump motor oil replenishment. On the basis of the hydraulic drive system jointly realized by the electric motor 3 and the hydraulic pump 2, the system introduces high pressure pump motor 15 and low pressure pump motor 17 to realize hydraulic oil replenishment and energy recovery energy-saving technology, which further improves the high frequency dynamic response and energy recovery capability of the forklift hydraulic system and realizes the efficient and stable operation of the system.

[0036] Based on the above embodiments, in an optional embodiment of the present invention, the control method of the forklift potential energy recovery system includes steps for lifting the forklift, steps for lowering the forklift, steps for recovering energy with a low-pressure pump motor, and steps for recovering energy with a high-pressure pump motor.

[0037] When the forklift forks are lifted, steps A1 through A5 are included.

[0038] A1. Use a sensor to determine the relationship between the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 and a first preset value and a second preset value. The first preset value is the low pressure threshold of the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9, and the second preset value is the medium pressure threshold of the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9. A2. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 does not exceed the first preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the fourth position, and the second two-position two-way solenoid directional valve 19 is opened so that the high-pressure pump motor 15 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, step A4 is executed directly. A3. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 is between the first preset value and the second preset value, control the five-position four-way hydraulic directional valve 14 to work in the fifth position and open the second two-position two-way solenoid directional valve 19 so that the low-pressure pump motor 17 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, directly execute step A4. A4. Connect the oil inlet of the three-position four-way solenoid directional valve 7 to the working outlet. The electric motor drives the hydraulic pump to supply the hydraulic oil in the hydraulic oil tank 1 to the oil circuit. The hydraulic oil passes through the first check valve 4, the throttle valve 6, and the three-position four-way solenoid directional valve 7 to enter the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 to realize the lifting motion of the forklift forks. A5. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 exceeds the second preset value, the first two-position two-way solenoid directional valve 12 is closed, the five-position four-way hydraulic directional valve 14 is controlled to work in the first position, and the second two-position two-way solenoid directional valve 19 is opened so that the hydraulic oil pressurized by the booster 11 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment.

[0039] When the forklift forks are lowered, steps B1 through B5 are included.

[0040] B1. Use a sensor to determine the relationship between the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 and the third preset value and the fourth preset value. The third preset value is the low pressure threshold of the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9, and the fourth preset value is the medium pressure threshold of the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9. B2. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 does not exceed the third preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the fourth position, and the second two-position two-way solenoid directional valve 19 is opened so that the high-pressure pump motor 15 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, step B4 is executed directly. B3. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 is between the third preset value and the fourth preset value, control the five-position four-way hydraulic directional valve 14 to work in the fifth position and open the second two-position two-way solenoid directional valve 19 so that the low-pressure pump motor 17 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment; otherwise, directly execute step B4. B4. Connect the oil inlet of the three-position four-way solenoid directional valve 7 to the working outlet. The electric motor drives the hydraulic pump to supply the hydraulic oil in the hydraulic oil tank 1 to the oil circuit. The hydraulic oil passes through the first check valve 4, the throttle valve 6, and the three-position four-way solenoid directional valve 7 to enter the rod chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 to realize the forklift fork lowering movement. B5. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 exceeds the fourth preset value, the first two-position two-way solenoid directional valve 12 is closed, the five-position four-way hydraulic directional valve 14 is controlled to work in the first position, and the second two-position two-way solenoid directional valve 19 is opened so that the hydraulic oil pressurized by the booster 11 is connected to the oil outlet of the hydraulic pump 2 for auxiliary oil replenishment.

[0041] When the low-pressure pump motor recovers potential energy, steps C1 to C3 are included.

[0042] C1. Use sensors to determine the relationship between the load of the forklift and the fifth and sixth preset values, and to determine whether the pressure of the low-pressure pump motor 17 is less than the seventh preset value. The fifth preset value is the low-pressure threshold of the forklift load, the sixth preset value is the medium-pressure threshold of the forklift load, and the seventh preset value is the maximum energy storage threshold of the low-pressure pump motor 17. C2. When it is determined that the load of the forklift is within the range of the fifth and sixth preset values, and the pressure of the low-pressure pump motor 17 is less than the seventh preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the third position, the first and second-position two-way solenoid directional valve 12 is opened, and the working outlet and return oil outlet of the three-position four-way solenoid directional valve 7 are connected, so that the hydraulic oil in the load of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 enters the low-pressure pump motor 17 under the action of the gravity of the goods through the three-position four-way solenoid directional valve 7, the two-position three-way solenoid directional valve 10, the first and second-position two-way solenoid directional valve 12, the second check valve 13 and the five-position four-way hydraulic directional valve 14, thereby realizing the recovery of gravitational potential energy. C3. When it is determined that the forklift load is less than the fifth preset value, open the two-position three-way solenoid directional valve 10 and connect the working outlet and return oil outlet of the three-position four-way solenoid directional valve 7, so that the hydraulic oil in the load of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 flows directly back to the hydraulic oil tank through the three-position four-way solenoid directional valve 7 and the two-position three-way solenoid directional valve 10 under the action of gravity.

[0043] Preferably, step C2 specifically includes steps C21 to C22.

[0044] C21. When it is determined that the load of the forklift is within the range of the fifth preset value and the sixth preset value, and the pressure of the low-pressure pump motor 17 is less than the seventh preset value, it is further determined whether the difference between the pressure of the forklift load and the pressure of the low-pressure pump motor 17 exceeds the ninth preset value. The ninth preset value is the minimum threshold value representing the difference between the forklift load and the low-pressure pump motor pressure. C22. Further determine that when the difference between the pressure of the forklift load and the pressure of the low-pressure pump motor 17 exceeds the ninth preset value, open the first two-position two-way solenoid directional valve 12 and control the five-position four-way hydraulic directional valve 14 to work in the third position, so that it connects in sequence to the oil outlet of the second check valve 13 and the oil outlet of the low-pressure pump motor 17, so that the hydraulic oil flows back to the low-pressure pump motor 17 through the first two-position two-way solenoid directional valve 12 and the five-position four-way hydraulic directional valve 14.

[0045] When the high-pressure pump motor recovers potential energy, steps D1 to D2 are included.

[0046] D1. Use sensors to determine the relationship between the load of the forklift and the fifth and sixth preset values, and determine whether the pressure of the high-pressure pump motor 15 is less than the eighth preset value, which is the highest threshold for the energy stored in the high-pressure pump motor. D2. When it is determined that the load of the forklift exceeds the sixth preset value and the pressure of the high-pressure pump motor 15 is less than the eighth preset value, the five-position four-way hydraulic directional valve 14 is controlled to work in the second position, the first two-position two-way solenoid directional valve 12 is opened, and the working outlet and return oil outlet of the three-position four-way solenoid directional valve 7 are connected, so that the hydraulic oil in the load of the first hydraulic cylinder 8 and the second hydraulic cylinder 9 enters the high-pressure pump motor 15 under the action of the gravity of the cargo through the three-position four-way solenoid directional valve 7, the two-position three-way solenoid directional valve 10, the first two-position two-way solenoid directional valve 12, the second check valve 13 and the five-position four-way hydraulic directional valve 14, so as to realize the recovery of gravitational potential energy; otherwise, execute C3.

[0047] Preferably, step D2 specifically includes steps D21 to D22.

[0048] D21. When it is determined that the load of the forklift exceeds the sixth preset value and the pressure of the high-pressure pump motor 15 is less than the eighth preset value, it is further determined whether the difference between the pressure of the forklift load and the pressure of the high-pressure pump motor 15 exceeds the tenth preset value. The tenth preset value is the minimum threshold representing the pressure difference between the forklift load and the high-pressure pump motor. D22. Further determine that when the difference between the pressure of the forklift load and the pressure of the high-pressure pump motor 15 exceeds the tenth preset value, open the first two-position two-way solenoid directional valve 12 and control the five-position four-way hydraulic directional valve 14 to work in the second position, so that it connects in sequence to the oil outlet of the second check valve 13 and the oil outlet of the high-pressure pump motor 15, so that the hydraulic oil flows back to the high-pressure pump motor 15 through the first two-position two-way solenoid directional valve 12 and the five-position four-way hydraulic directional valve 14.

[0049] Specifically, the present invention discloses a forklift potential energy recovery system based on high and low pressure pump motors for oil replenishment. This system utilizes a high-pressure pump motor 15 and a low-pressure pump motor 17 to recover energy for secondary use, improving energy efficiency. Combined with the pressurizing effect of a booster 11, it achieves rapid oil replenishment. This effectively solves the problems of high energy consumption, low energy efficiency, and slow dynamic response in traditional forklift fork systems.

[0050] Based on the above embodiments, in an optional embodiment of the present invention, the forklift potential energy recovery system includes multiple energy storage components such as a booster, a high-pressure pump motor, and a low-pressure pump motor, and the loads of the two hydraulic cylinders and the energy storage components are respectively set with different preset values. During energy recovery, the potential energy is recovered sequentially from low to high based on the load pressure of the two hydraulic cylinders and compared with the different preset values.

[0051] Based on the above embodiments, in an optional embodiment of the present invention, two preset values ​​are set for the load of the hydraulic cylinder. Multiple pressure levels are set from small to large according to whether the recovered oil eventually flows to the hydraulic oil tank 1, the low-pressure pump motor 17 and the high-pressure pump motor 15. Each pressure level corresponds to a type of energy recovery.

[0052] Specifically, the preset values ​​of each actuator, as well as the specific values ​​of the fifth and sixth preset values ​​for different pressure levels of the forklift load, shall be set by those skilled in the art according to the actual situation, and the present invention does not impose specific limitations on them.

[0053] This invention discloses a forklift potential energy recovery system based on high and low pressure pump motor replenishment. A high-pressure pump motor 15 and a low-pressure pump motor 17 are sequentially connected to a five-position four-way hydraulic directional valve 14. Different potential energy recovery oil circuits are separated using a two-position two-way solenoid directional valve and the five-position four-way hydraulic directional valve 14. Based on the hydraulic cylinder load pressure, multiple hydraulic components work together to recover forklift potential energy, maximizing energy recovery and significantly improving energy utilization. Simultaneously, the pump motor drive and the booster 11 pressurize the system, rapidly replenishing the recovered potential energy to the working oil circuit, optimizing the dynamic response of the forklift system and making its operation more stable and efficient.

[0054] This application also provides a forklift that includes a forklift potential energy recovery system based on high and low pressure pump motor oil replenishment as described in any paragraph of the first aspect.

[0055] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A forklift potential energy recovery system based on high and low pressure pump motor oil replenishment, characterized in that, It includes a lifting oil circuit, a lowering oil circuit, a potential energy recovery oil circuit, and an auxiliary oil replenishment oil circuit; The lifting oil circuit includes a hydraulic oil tank (1), a hydraulic pump (2), an electric motor (3), a first check valve (4), a throttle valve (6), and a three-position four-way solenoid valve (7). The hydraulic oil tank (1) is connected to the oil inlet of the hydraulic pump (2). The shaft of the hydraulic pump (2) is connected to the electric motor (3). The oil outlet of the hydraulic pump (2) is connected to the oil inlet of the first check valve (4). The oil outlet of the first check valve (4) is connected to the inlet of the throttle valve (6). The outlet of the throttle valve (6) is connected to the P port of the three-position four-way solenoid valve (7). The A port of the three-position four-way solenoid valve (7) is connected to the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9). The first hydraulic cylinder (8) and the second hydraulic cylinder (9) are used to drive the forks to rise. The lowering oil circuit includes a hydraulic oil tank (1), a hydraulic pump (2), an electric motor (3), a first check valve (4), a throttle valve (6), and a three-position four-way solenoid directional valve (7); the B port of the three-position four-way solenoid directional valve (7) is connected to the rod chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9); wherein, the first hydraulic cylinder (8) and the second hydraulic cylinder (9) are used to drive the forks to lower. The potential energy recovery oil circuit includes a two-position three-way solenoid directional valve (10), a first two-position two-way solenoid directional valve (12), a second check valve (13), a five-position four-way hydraulic directional valve (14), a high-pressure pump motor (15), and a low-pressure pump motor (17); the T-port of the three-position four-way solenoid directional valve (7) is connected to the oil inlet of the two-position three-way solenoid directional valve (10); the oil outlet of the two-position three-way solenoid directional valve (10) is connected to the first two-position two-way solenoid valve. The oil inlet of the solenoid directional valve (12); the oil outlet of the first two-position two-way solenoid directional valve (12) is connected to the oil inlet of the second check valve (13); the five-position four-way hydraulic directional valve (14) is sequentially connected to the oil outlet of the second check valve (13), the oil outlet of the high-pressure pump motor (15) and the oil outlet of the low-pressure pump motor (17); the oil inlet of the high-pressure pump motor (15) and the oil inlet of the low-pressure pump motor (17) are connected to the hydraulic oil tank (1); The auxiliary oil supply circuit includes a two-position three-way solenoid directional valve (10), a booster (11), a first two-position two-way solenoid directional valve (12), a second check valve (13), a five-position four-way hydraulic directional valve (14), a second two-position two-way solenoid directional valve (19), and a third check valve (20). The five-position four-way hydraulic directional valve (14) is connected to the oil outlet of the second check valve (13) and the oil inlet of the second two-position two-way solenoid directional valve (19) in sequence. The oil outlet of the second two-position two-way solenoid directional valve (19) is connected to the oil inlet of the third check valve (20), and the oil outlet of the third check valve (20) is connected to the oil outlet of the first check valve (4).

2. The forklift potential energy recovery system based on high and low pressure pump motor oil replenishment according to claim 1, characterized in that, The lifting and lowering oil circuits also include a first relief valve (5), the inlet of which is connected to the outlet of the first check valve (4), and the outlet of which is connected to the hydraulic oil tank (1).

3. The forklift potential energy recovery system based on high and low pressure pump motor oil replenishment according to claim 1, characterized in that, The first hydraulic cylinder (8) and the second hydraulic cylinder (9) are connected in parallel. The rod chamber of the first hydraulic cylinder (8) is connected to the rod chamber of the second hydraulic cylinder (9), and the rodless chamber of the first hydraulic cylinder (8) is connected to the rodless chamber of the second hydraulic cylinder (9).

4. The forklift potential energy recovery system based on high and low pressure pump motor oil replenishment according to claim 1, characterized in that, The potential energy recovery oil circuit also includes a second overflow valve (16), the oil inlet of which is connected to the oil outlet of the high pressure pump motor (15), and the oil outlet of which is connected to the hydraulic oil tank (1).

5. The forklift potential energy recovery system based on high and low pressure pump motor oil replenishment according to claim 1, characterized in that, The potential energy recovery oil circuit also includes a third relief valve (18), the oil inlet of which is connected to the oil outlet of the low-pressure pump motor (17), and the oil outlet of which is connected to the hydraulic oil tank.

6. A method for recovering potential energy from a forklift based on oil replenishment from a high- and low-pressure pump motor, characterized in that, It employs the forklift potential energy recovery system as described in any one of claims 1-5, wherein the method for lifting the forklift forks specifically comprises: A1. Use a sensor to determine the relationship between the pressure in the rod chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) and the first preset value and the second preset value. The first preset value is the low pressure threshold of the rod chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9), and the second preset value is the medium pressure threshold of the rod chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9). A2. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) does not exceed the first preset value, control the five-position four-way hydraulic directional valve (14) to work in the fourth position and open the second two-position two-way solenoid directional valve (19) so that the high-pressure pump motor (15) is connected to the oil outlet of the hydraulic pump (2) for auxiliary oil replenishment; otherwise, directly execute step A4. A3. When it is determined that the pressure in the rod chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) is between the first preset value and the second preset value, control the five-position four-way hydraulic directional valve (14) to work in the fifth position and open the second two-position two-way solenoid directional valve (19) so that the low-pressure pump motor (17) is connected to the oil outlet of the hydraulic pump (2) for auxiliary oil replenishment; otherwise, directly execute step A4. A4. Connect the oil inlet of the three-position four-way solenoid directional valve (7) to the working outlet. The electric motor drives the hydraulic pump to supply the hydraulic oil in the hydraulic oil tank (1) to the oil circuit. The hydraulic oil passes through the first check valve (4), the throttle valve (6), and the three-position four-way solenoid directional valve (7) to enter the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) to realize the lifting motion of the forklift forks. A5. When it is determined that the rod chamber pressure of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) exceeds the second preset value, the first two-position two-way solenoid directional valve (12) is closed, the five-position four-way hydraulic directional valve (14) is controlled to work in the first position, and the second two-position two-way solenoid directional valve (19) is opened so that the hydraulic oil pressurized by the booster (11) is connected to the oil outlet of the hydraulic pump (2) for auxiliary oil replenishment.

7. The forklift potential energy recovery method based on high and low pressure pump motor oil replenishment according to claim 6, characterized in that, The specific method for lowering the forklift forks is as follows: B1. Use a sensor to determine the relationship between the pressure in the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) and the third preset value and the fourth preset value. The third preset value is the low pressure threshold of the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9), and the fourth preset value is the medium pressure threshold of the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9). B2. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) does not exceed the third preset value, control the five-position four-way hydraulic directional valve (14) to work in the fourth position and open the second two-position two-way solenoid directional valve (19) so that the high-pressure pump motor (15) is connected to the oil outlet of the hydraulic pump (2) for auxiliary oil replenishment; otherwise, directly execute step B4. B3. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) is between the third preset value and the fourth preset value, control the five-position four-way hydraulic directional valve (14) to work in the fifth position and open the second two-position two-way solenoid directional valve (19) so that the low-pressure pump motor (17) is connected to the oil outlet of the hydraulic pump (2) for auxiliary oil replenishment; otherwise, directly execute step B4. B4. Connect the oil inlet of the three-position four-way solenoid directional valve (7) to the working outlet. The electric motor drives the hydraulic pump to supply the hydraulic oil in the hydraulic oil tank (1) to the oil circuit. The hydraulic oil passes through the first check valve (4), the throttle valve (6), and the three-position four-way solenoid directional valve (7) to enter the rod chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) to realize the forklift fork lowering movement. B5. When it is determined that the pressure in the rodless chamber of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) exceeds the fourth preset value, the first two-position two-way solenoid directional valve (12) is closed, the five-position four-way hydraulic directional valve (14) is controlled to work in the first position, and the second two-position two-way solenoid directional valve (19) is opened so that the hydraulic oil pressurized by the booster (11) is connected to the oil outlet of the hydraulic pump (2) for auxiliary oil replenishment.

8. The forklift potential energy recovery method based on high and low pressure pump motor oil replenishment according to claim 7, characterized in that, The specific method for recovering potential energy from the low-pressure pump motor is as follows: C1. Use sensors to determine the relationship between the load of the forklift and the fifth and sixth preset values, and to determine whether the pressure of the low-pressure pump motor (17) is less than the seventh preset value. The fifth preset value is the low-pressure threshold of the forklift load, the sixth preset value is the medium-pressure threshold of the forklift load, and the seventh preset value is the highest energy storage threshold of the low-pressure pump motor (17). C2. When it is determined that the load of the forklift is within the range of the fifth and sixth preset values, and the pressure of the low-pressure pump motor (17) is less than the seventh preset value, the five-position four-way hydraulic directional valve (14) is controlled to work in the third position, the first two-position two-way solenoid directional valve (12) is opened, and the working outlet and return oil outlet of the three-position four-way solenoid directional valve (7) are connected, so that the hydraulic oil in the load of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) enters the low-pressure pump motor (17) under the action of the gravity of the goods through the three-position four-way solenoid directional valve (7), the two-position three-way solenoid directional valve (10), the first two-position two-way solenoid directional valve (12), the second check valve (13) and the five-position four-way hydraulic directional valve (14), thereby realizing the recovery of gravitational potential energy. C3. When it is determined that the load of the forklift is less than the fifth preset value, open the two-position three-way solenoid directional valve (10) and connect the working outlet and return oil outlet of the three-position four-way solenoid directional valve (7) so that the hydraulic oil in the load of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) flows directly back to the hydraulic oil tank through the three-position four-way solenoid directional valve (7) and the two-position three-way solenoid directional valve (10) under the action of gravity.

9. The forklift potential energy recovery method based on high and low pressure pump motor oil replenishment according to claim 8, characterized in that, The specific method for recovering potential energy using a high-pressure pump motor is as follows: D1. Use sensors to determine the relationship between the load of the forklift and the fifth and sixth preset values, and determine whether the pressure of the high-pressure pump motor (15) is less than the eighth preset value, where the eighth preset value is the highest threshold for the energy stored in the high-pressure pump motor. D2. When it is determined that the load of the forklift exceeds the sixth preset value and the pressure of the high-pressure pump motor (15) is less than the eighth preset value, control the five-position four-way hydraulic directional valve (14) to work in the second position, open the first two-position two-way solenoid directional valve (12), and connect the working outlet and return oil outlet of the three-position four-way solenoid directional valve (7) so that the hydraulic oil in the load of the first hydraulic cylinder (8) and the second hydraulic cylinder (9) enters the high-pressure pump motor (15) through the three-position four-way solenoid directional valve (7), the two-position three-way solenoid directional valve (10), the first two-position two-way solenoid directional valve (12), the second check valve (13) and the five-position four-way hydraulic directional valve (14) under the action of the gravity of the goods, so as to realize the recovery of gravitational potential energy. Otherwise, execute C3.

10. The forklift potential energy recovery method based on high and low pressure pump motor oil replenishment according to claim 8, characterized in that, C2 specifically includes: C21. When it is determined that the load of the forklift is within the range of the fifth preset value and the sixth preset value, and the pressure of the low-pressure pump motor (17) is less than the seventh preset value, it is further determined whether the difference between the pressure of the forklift load and the pressure of the low-pressure pump motor (17) exceeds the ninth preset value. The ninth preset value is the minimum threshold value representing the difference between the forklift load and the low-pressure pump motor pressure. C22. Further determine that when the difference between the pressure of the forklift load and the pressure of the low-pressure pump motor (17) exceeds the ninth preset value, open the first two-position two-way solenoid directional valve (12) and control the five-position four-way hydraulic directional valve (14) to work in the third position, so that it connects the oil outlet of the second check valve (13) and the oil outlet of the low-pressure pump motor (17) in sequence, so that the hydraulic oil flows back to the low-pressure pump motor (17) through the first two-position two-way solenoid directional valve (12) and the five-position four-way hydraulic directional valve (14).

11. The forklift potential energy recovery method based on high and low pressure pump motor oil replenishment according to claim 9, characterized in that, Specifically, D2 includes: D21. When it is determined that the load of the forklift exceeds the sixth preset value and the pressure of the high-pressure pump motor (15) is less than the eighth preset value, it is further determined whether the difference between the pressure of the forklift load and the pressure of the high-pressure pump motor (15) exceeds the tenth preset value. The tenth preset value is the minimum threshold representing the pressure difference between the forklift load and the high-pressure pump motor. D22. Further determine that when the difference between the pressure of the forklift load and the pressure of the high-pressure pump motor (15) exceeds the tenth preset value, open the first two-position two-way solenoid directional valve (12) and control the five-position four-way hydraulic directional valve (14) to work in the second position, so that it connects the oil outlet of the second check valve (13) and the oil outlet of the high-pressure pump motor (15) in sequence, so that the hydraulic oil flows back to the high-pressure pump motor (15) through the first two-position two-way solenoid directional valve (12) and the five-position four-way hydraulic directional valve (14).

12. A forklift, characterized in that, Including the forklift potential energy recovery system based on high and low pressure pump motor oil replenishment as described in any one of claims 1-5.

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